An image sensor includes a semiconductor substrate, a first pair of photoelectric conversion regions in a first pixel region of the substrate and a first isolation structure between the photoelectric conversion regions of the first pair of photoelectric conversion regions. The sensor further includes a second pair of photoelectric conversion regions in a second pixel region of the substrate adjacent the first pixel region and a second isolation structure between the photoelectric conversion regions of the second pair of photoelectric conversion regions and having different optical properties than the first isolation structure. First and second different color filters (e.g., green and red) may be disposed on respective ones of the first and second pixel regions.